It has been quite amazing to watch the global excitement build around Windows 7, especially during a tough economic climate. It was just a few short weeks ago that we learned about Windows 7 outselling the UK’s “own” Harry Potter. In Japan, anxious PC users waited in line to be one of the first to get their hands on Windows 7. And just today, according to the NPD groups’ weekly tracking service, Windows 7 software unit sales in the U.S. increased 234% over Windows Vista’s first few days of sales. “A combination of factors impacted Windows 7 PC sales at the outset, but the trajectory of overall PC sales is very strong leading into the holiday season,” said Stephen Baker at NPD.